Autostereoscopic display for multiple viewers

ABSTRACT

An apparatus for displaying a stereoscopic virtual image to a first viewer ( 12   a ) and to a second viewer ( 12   b ), where the stereoscopic virtual image is imaged to each viewer at a left viewing pupil ( 14   l ) and a right viewing pupil ( 14   r ). Configurations using multiple beamsplitters ( 16 ) and one or two curved mirrors ( 24 ) direct the optical path to first and second viewers ( 12   a  and  12   b ).

CROSS REFERENCE TO RELATED APPLICATIONS

Reference is made to commonly-assigned copending U.S. patent applicationSer. No. 10/393,236, filed Mar. 20, 2003, entitled METHOD AND APPARATUSFOR MONOCENTRIC PROJECTION OF AN IMAGE, by Joshua M. Cobb and U.S.patent application Ser. No. 10/465,503, filed Jun. 19, 2003, entitledMETHOD AND APPARATUS FOR FORMING AN IMAGE ON A CURVED DIFFUSIVE SURFACE,by Liang et al., the disclosures of which are incorporated herein.

FIELD OF THE INVENTION

This invention generally relates to display apparatus and moreparticularly relates to an apparatus and method for autostereoscopicdisplay to multiple viewers.

BACKGROUND OF THE INVENTION

The potential value of autostereoscopic display systems is widelyappreciated particularly in entertainment and simulation fields.Autostereoscopic display systems include “immersion” systems, intendedto provide a realistic viewing experience for an observer by visuallysurrounding the observer with a three-dimensional (3-D) image having avery wide field of view. As differentiated from the larger group ofstereoscopic displays that include it, the autostereoscopic display ischaracterized by the absence of any requirement for a wearable item ofany type, such as goggles, headgear, or special glasses, for example.That is, an autostereoscopic display attempts to provide “natural”viewing conditions for an observer.

One example autostereoscopic system is disclosed in commonly-assignedU.S. Pat. No. 6,416,181 (Kessler et al.), incorporated herein byreference, herein referred to as the '181 patent. In an autostereoscopicprojection apparatus 10 as described in the '181 disclosure and as shownin FIG. 1, a curved mirror 24 is employed, in combination with abeamsplitter 16 for providing an autostereoscopic virtual image to aviewer 12 at left and right viewing pupils 14 l and 14 r. For left andright viewing pupil 14 l and 14 r, a corresponding image generationsystem 70 l and 70 r provides an initial intermediate curved image thatis then projected through a ball lens segment 30 in order to form a leftor right intermediate curved image 80 l or 80 r at a focal plane ofcurved mirror 24.

The substantially monocentric optical apparatus of the '181 disclosureprovides realistic autostereoscopic imaging with large viewing pupils, avery wide field of view, and minimal aberration. However, one salientlimitation of the apparatus represented in FIG. 1 is its constraint touse by only one viewer 12 at a time. While this arrangement may besuitable for some types of simulator or entertainment applications,there can be applications where it is advantageous, and morecost-effective, to provide autostereoscopic images to a second viewer12.

Autostereoscopic display systems for multiple viewers have beenproposed, including the following:

-   -   U.S. Pat. No. 6,449,090 (Omar et al.) discloses a dual-function        apparatus that can be used to provide an autostereoscopic image        to a single viewer and stereoscopic images to multiple viewers,        each of whom, however, requires a polarizing or shuttering        device; and    -   European Patent Specification EP 0 602 934 discloses an        autostereoscopic display apparatus that provides a real image        simultaneously to two observers. One shortcoming of this        approach for many types of display applications relates to the        separation of left- and right-eye images; in a disclosed        embodiment, right- and left-eye images are reversed for the two        observers.

For fully satisfactory 3-D viewing, an autostereoscopic display systemshould provide separate, high-resolution images to right and left eyes.It can also be readily appreciated that such a system is most favorablydesigned for compactness, creating an illusion of depth and width offield, while occupying as little actual floor space and volume as ispossible. For the most realistic viewing experience, the observer shouldbe presented with a virtual image, disposed to appear a large distanceaway. Thus, it can be seen that there is a need for an autostereoscopicimaging subsystem using pupil imaging that provides virtual images formultiple viewers.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an autostereoscopicdisplay apparatus that can be viewed by multiple viewers. With thisobject in mind, the present invention provides an autostereoscopicoptical apparatus for displaying a stereoscopic virtual image to a firstviewer and to a second viewer, wherein the stereoscopic virtual image isimaged to each viewer at a left viewing pupil and a right viewing pupil,the apparatus comprising:

-   -   (a) a left image generation system for forming a curved left        intermediate image;    -   (b) a left projection system comprising a left ball lens        segment, wherein the pupil of the left ball lens segment is        substantially concentric with the curved left intermediate        image, the left ball lens segment forming a real image of the        curved left intermediate image;    -   (c) a first beamsplitter disposed to direct the curved left        intermediate image toward a focal surface of a first curved        mirror, the first curved mirror forming a virtual image of the        curved left intermediate image thereby, and the first curved        mirror disposed to form:        -   (i) through the first beamsplitter, a real image of the            pupil of the left ball lens segment at the left viewing            pupil of the first viewer; and        -   (ii) through a second beamsplitter, a real image of the            pupil of the left ball lens segment at the left viewing            pupil of the second viewer;    -   (d) a right image generation system for forming a curved right        intermediate image;    -   (e) a right projection system comprising a right ball lens        segment, wherein the pupil of the right ball lens segment is        substantially concentric with the curved right intermediate        image, the right ball lens segment forming a real image of the        curved right intermediate image;    -   (f) a third beamsplitter disposed to direct the curved right        intermediate image toward a focal surface of a second curved        mirror, the second curved mirror forming a virtual image of the        curved right intermediate image thereby, and the second curved        mirror disposed to form:        -   (i) through the third beamsplitter, a real image of the            pupil of the right ball lens segment at the right viewing            pupil of the second viewer; and        -   (ii) through the second beamsplitter, a real image of the            pupil of the right ball lens segment at the right viewing            pupil of the first viewer.

It is a feature of the present invention that it utilizes light that isotherwise unused for a single-viewer autostereoscopic immersion system.The system is essentially monocentric, inherently minimizing imageaberrations.

It is an advantage of the present invention that it provides, from asingle display apparatus full autostereoscopic viewing for at least twoviewers.

These and other objects, features, and advantages of the presentinvention will become apparent to those skilled in the art upon areading of the following detailed description when taken in conjunctionwith the drawings wherein there is shown and described an illustrativeembodiment of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

While the specification concludes with claims particularly pointing outand distinctly claiming the subject matter of the present invention, itis believed that the invention will be better understood from thefollowing description when taken in conjunction with the accompanyingdrawings, wherein:

FIG. 1 is a perspective view showing a prior art autostereoscopicoptical apparatus for display to a single viewer;

FIG. 2 a is schematic view showing the optical paths for a displayapparatus serving multiple viewers simultaneously;

FIG. 2 b is a perspective view showing an arrangement of opticalcomponents corresponding to the schematic view of FIG. 2 a;

FIG. 3 a is schematic view showing the optical paths for anotherembodiment of a display apparatus serving multiple viewerssimultaneously, using a single mirror;

FIG. 3 b is a perspective view showing an arrangement of opticalcomponents corresponding to the schematic view of FIG. 3 a;

FIG. 4 a is schematic view showing the optical paths for yet anothersingle-curved-mirror embodiment of a display apparatus for a displayapparatus serving multiple viewers simultaneously;

FIG. 4 b is a perspective view showing an arrangement of opticalcomponents corresponding to the schematic view of FIG. 4 a;

FIG. 5 a is schematic view showing the optical paths for yet anotheralternative display apparatus serving multiple viewers simultaneously;

FIG. 5 b is a perspective view showing an arrangement of opticalcomponents corresponding to the schematic view of FIG. 5 a;

FIG. 6 a is schematic view showing the optical paths for yet anotheralternative display apparatus using a single curved mirror to servemultiple viewers simultaneously; and

FIG. 6 b is a perspective view showing an arrangement of opticalcomponents corresponding to the schematic view of FIG. 6 a.

DETAILED DESCRIPTION OF THE INVENTION

The present description is directed in particular to elements formingpart of, or cooperating more directly with, apparatus in accordance withthe invention. It is to be understood that elements not specificallyshown or described may take various forms well known to those skilled inthe art.

The disclosure of U.S. Pat. No. 6,416,181 and U.S. patent applicationSer. Nos. 10/393,236 and 10/465,503 give detailed information on how anintermediate image can be formed using a linear or an area spatial lightmodulator. The description of the present invention that followsconcerns itself with the optical path that, given these left and rightintermediate images, forms left and right virtual images in order toprovide an apparatus allowing multiple viewers.

Embodiments with Multiple Curved Mirrors 24

Referring to FIG. 2 a, there is shown, in side-view schematic form, anembodiment of a multi-viewer autostereoscopic imaging apparatus 100employing a left curved mirror 24 l for providing an image to leftpupils 14 l of viewers 12 a and 12 b. In the optical path for both leftpupils 14 l, a left intermediate image 76 l is generated from left imagegeneration system 70 l, as shown in FIG. 1 and described in the '181disclosure. Left ball lens segment 30 l may be a ball lens componentcomprising a fully spherical lens or may be an hemispheric lens segmenthaving a reflective surface, as is disclosed in commonly-assigned U.S.Pat. No. 6,511,182 (Agostinelli et al.), incorporated herein byreference. Left intermediate image 76 l is projected by left ball lenssegment 30 l and reflected from a beamsplitter 16 a to the focal surfaceof left curved mirror 24 l as a real image. The resulting collimatedleft virtual image is then viewed by viewer 12 a at left viewing pupil14 l. A second beamsplitter 16 b cooperates with a third beamsplitter 16c to direct the collimated left virtual image to left viewing pupil 14 lof viewer 12 b.

From the schematic view of FIG. 2 a, the optical path to left viewingpupil 14 l for viewer 12 a can be traced through the following points:

-   -   Channel I→P1→P2→P4→P2→P1→Left viewing pupil 14 l        The optical path to left viewing pupil 14 l for viewer 12 b can        be traced through the following points:    -   Channel I→P1→P2→P4→P2→P5→Left viewing pupil 14 l        The optical path for both right pupils 14 r of viewers 12 a and        12 b begins with right intermediate image 76 r, employs a curved        mirror 24 r and beamsplitters 16 a, 16 b, and 16 c, and can be        similarly traced. From the schematic view of FIG. 2 a, the        optical path to right viewing pupil 14 r for viewer 12 a can be        traced through the following points:    -   Channel II→P5→P2→P3→P2→P1→Right viewing pupil 14 r        The optical path to right viewing pupil 14 r for viewer 12 b can        be traced through the following points:    -   Channel II→P5→P2→P3→P2→P5→Right viewing pupil 14 r

Referring to FIG. 2 b, there is shown a perspective view of opticalcomponents corresponding to the arrangement of FIG. 2 a.

A second embodiment using multiple curved mirrors 24 l and 24 r is shownin FIGS. 5 a and 5 b. In this alternate arrangement, ball lens segments30 l and 30 r are located close together, as is shown most clearly inthe perspective view of FIG. 5 b. Only two beamsplitters 16 a and 16 bare required. A folding mirror 82 is used for directing the light pathto viewer 12 b.

From the schematic view of FIG. 5 a, the optical path to left viewingpupil 14 l for viewer 12 a can be traced through the following points:

-   -   Channel I→P1→P2→P3→P2→P1→Left viewing pupil 14 l        The optical path to left viewing pupil 14 l for viewer 12 b can        be traced through the following points:    -   Channel I→P1→P2→P3→P2→P5→Left viewing pupil 14 l

From the schematic view of FIG. 5 a, the optical path to right viewingpupil 14 r for viewer 12 a can be traced through the following points:

-   -   Channel II→P1→P2→P4→P2→P1→Right viewing pupil 14 r        The optical path to right viewing pupil 14 r for viewer 12 b can        be traced through the following points:    -   Channel II→P1→P2→P4→P2→P5→Right viewing pupil 14 r        Embodiments with a Single Curved Mirror 24

Referring to FIG. 3 a, there is shown, in side-view schematic form, anembodiment of a multi-viewer autostereoscopic imaging apparatus 100employing a single curved mirror 24 for providing images at both leftand right pupils 14 l and 14 r for viewers 12 a and 12 b. In the opticalpath for both left pupils 14 l, a left intermediate image 76 l isgenerated from left image generation system 70 l (not shown in FIG. 3a). Left intermediate image 76 l is projected by left ball lens segment30 l and reflected from first beamsplitter 16 a to second beamsplitter16 b near the focal surface of left curved mirror 24 l, as a real image.The resulting collimated left virtual image is then reflected fromsecond beamsplitter 16 b and, through first beamsplitter 16 a can beviewed by viewer 12 a at left viewing pupil 14 l. Second beamsplitter 16b also cooperates with third beamsplitter 16 c to direct the collimatedleft virtual image to left viewing pupil 14 l of viewer 12 b.

From the schematic view of FIG. 3 a, the optical path to left viewingpupil 14 l for viewer 12 a can be traced through the following points:

-   -   Channel I→P1→P2→P3→P2→P1→Left viewing pupil 14 l        The optical path to left viewing pupil 14 l for viewer 12 b can        be traced through the following points:    -   Channel I→P1→P2→P3→P2→P5→Left viewing pupil 14 l

From the schematic view of FIG. 3 a, the optical path to right viewingpupil 14 r for viewer 12 a can be traced through the following points:

-   -   Channel II→P5→P2→P3→P2→P1→Right viewing pupil 14 r        The optical path to right viewing pupil 14 r for viewer 12 b can        be traced through the following points:    -   Channel II→P5→P2→P3→P2→P5→Right viewing pupil 14 r

Referring to FIG. 3 b, there is shown a perspective view of opticalcomponents corresponding to the arrangement of FIG. 3 a.

Referring to FIGS. 4 a and 4 b, there is shown an alternate arrangementfor multi-viewer autostereoscopic imaging apparatus 100 using one curvedmirror 24, with folding mirror 82 added. From the schematic view of FIG.4 a, the optical path to left viewing pupil 14 l for viewer 12 a can betraced through the following points:

-   -   Channel I→P1→P2→P3→P2→P→Left viewing pupil 14 l        The optical path to left viewing pupil 14 l for viewer 12 b can        be traced through the following points:    -   Channel I→P1→P2→P3→P2→P4→P5→Left viewing pupil 14 l

From the schematic view of FIG. 4 a, the optical path to right viewingpupil 14 r for viewer 12 a can be traced through the following points:

-   -   Channel II→P4→P2→P3→P2→P1→Right viewing pupil 14 r        The optical path to right viewing pupil 14 r for viewer 12 b can        be traced through the following points:    -   Channel II→P4→P2→P3→P2→P4→P5→Right viewing pupil 14 r

Yet another embodiment using one curved mirror 24 is shown in FIGS. 6 aand 6 b. In this alternate arrangement, ball lens segments 30 l and 30 rare located close together, as is shown most clearly in the perspectiveview of FIG. 6 b. Only two beamsplitters 16 a and 16 b are required.Folding mirror 82 is used for directing the imaging light path to viewer12 b.

From the schematic view of FIG. 6 a, the optical path to left viewingpupil 14 l for viewer 12 a can be traced through the following points:

-   -   Channel I→P1→P2→P4→P2→P1→Left viewing pupil 14 l        The optical path to left viewing pupil 14 l for viewer 12 b can        be traced through the following points:    -   Channel I→P1→P2→P3→P2→P5→Left viewing pupil 14 l

From the schematic view of FIG. 6 a, the optical path to right viewingpupil 14 r for viewer 12 a can be traced through the following points:

-   -   Channel II→P1→P2→P4→P2→P1→Right viewing pupil 14 r        The optical path to right viewing pupil 14 r for viewer 12 b can        be traced through the following points:    -   Channel II→P1→P2→P4→P2→P5Right viewing pupil 14 r

As is noted hereinabove, embodiments shown in FIGS. 2 b, 3 b, 4 b, 5 b,and 6 b depict ball lens segments 30 l, 30 r as spherical; however, withany of these configurations, one or both ball lens segments 30 l, 30 rcould use a hemispheric lens segment having a reflective surface.

Advantages and Tradeoffs for Embodiments Shown

The embodiments shown in FIGS. 2 b, 3 b, 4 b, 5 b, and 6 b use differentarrangements of curved mirror 24 and left and right ball lens segment 30l and 30 r. It is instructive to note some advantages and drawbackspresented by the various design approaches shown in these figures. Asadvantages, designs using a single curved mirror 24, as shown in FIGS. 3a, 3 b, 4 a, 4 b, 6 a, and 6 b, use fewer components and allow a longerworking distance. Among disadvantages where using a single curved mirror24 are off-axis anomalies for forming left and right viewing pupils 14 land 14 r. For each viewer 12, both left and right optical paths must beslightly off-axis with respect to curved mirror 24. This causes a slightkeystoning aberration in each optical path, with keystoning in oppositedirections between left and right images. To some extent, this effectcan be corrected electronically.

Designs using left and right curved mirrors 24 l and 24 r, such as thoseshown in FIGS. 2 a, 2 b, 5 a, and 5 b allow on-axis imaging, minimizingor eliminating keystoning effects. However, designs using multiplemirrors are disadvantaged due to mechanical placement constraints; it isdifficult to arrange both left and right curved mirrors 24 l and 24 rwithout some obstruction and consequent reduction of field width.

Another design consideration relates to the relative positioning of leftand right ball lens segments 30 l and 30 r. In the embodiments of FIGS.2 b, 3 b, and 4 b, both left and right ball lens segments 30 l and 30 rcan be separately positioned, with a relatively large distance betweenthem. This arrangement eases space requirements for imaging supportcomponents and allows the size of ball lens segment 30 components to berelatively larger, providing a larger viewing pupil 14. By contrast, theembodiments of FIGS. 5 b and 6 b require that ball lens segments 30 land 30 r be positioned closely together, but allow a more compact designoverall.

The invention has been described in detail with particular reference tocertain preferred embodiments thereof, but it will be understood thatvariations and modifications can be effected within the scope of theinvention as described above, and as noted in the appended claims, by aperson of ordinary skill in the art without departing from the scope ofthe invention. For example, a number of different image generationsystem 70 configurations could be employed, using either scanned linearspatial light modulators or area spatial light modulators. Examples ofscanned linear spatial light modulators include grating light valve(GLV) linear arrays, as described in U.S. Pat. No. 5,311,360 (Bloom etal.) and conformal grating electromechanical system (GEMS) components,as disclosed in commonly-assigned U.S. Pat. No. 6,307,663 (Kowarz).Examples of area spatial light modulators include liquid crystal device(LCD) or digital micromirror device (DMD) components, both well known inthe digital imaging arts.

The curved image formed as left or right intermediate image 76 l, 76 rcould be formed on a diffusive surface, as was described in the '181disclosure, or could be formed using techniques disclosed in copendingapplications noted above, U.S. patent application Ser. Nos. 10/393,236and 10/465,503.

Thus, what is provided is an autostereoscopic display apparatus andmethod for providing a virtual image display using pupil imaging tomultiple viewers.

Parts List

-   10 autostereoscopic imaging apparatus-   12 viewer-   12 a viewer-   12 b viewer-   14 viewing pupil-   14 l viewing pupil, left-   14 r viewing pupil, right-   16 beamsplitter-   16 a beamsplitter-   16 b beamsplitter-   16 c beamsplitter-   24 curved mirror-   24 l left curved mirror-   24 r right curved mirror-   30 ball lens segment-   30 l left ball lens segment-   30 r right ball lens segment-   70 image generation system-   70 l left image generation system-   70 r right image generation system-   76 l left intermediate image-   76 r right intermediate image-   80 intermediate curved image-   80 l intermediate curved image, left-   80 r intermediate curved image, right-   82 folding mirror-   100 multi-viewer autostereoscopic imaging apparatus

1. An autostereoscopic optical apparatus for displaying a stereoscopicvirtual image to a first viewer and to a second viewer, wherein thestereoscopic virtual image is imaged to each viewer at a left viewingpupil and a right viewing pupil, the apparatus comprising: (a) a leftimage generation system for forming a curved left intermediate image;(b) a left projection system comprising a left ball lens segment,wherein the pupil of said left ball lens segment is substantiallyconcentric with said curved left intermediate image, said left ball lenssegment forming a real image of said curved left intermediate image; (c)a first beamsplitter disposed to direct said curved left intermediateimage toward a focal surface of a first curved mirror, said first curvedmirror forming a virtual image of said curved left intermediate imagethereby, and said first curved mirror disposed to form: (i) through saidfirst beamsplitter, a real image of the pupil of said left ball lenssegment at the left viewing pupil of the first viewer; and (ii) througha second beamsplitter, a real image of the pupil of said left ball lenssegment at the left viewing pupil of the second viewer; (d) a rightimage generation system for forming a curved right intermediate image;(e) a right projection system comprising a right ball lens segment,wherein the pupil of said right ball lens segment is substantiallyconcentric with said curved right intermediate image, said right balllens segment forming a real image of said curved right intermediateimage; (f) a third beamsplitter disposed to direct said curved rightintermediate image toward a focal surface of a second curved mirror,said second curved mirror forming a virtual image of said curved rightintermediate image thereby, and said second curved mirror disposed toform: (i) through said third beamsplitter, a real image of the pupil ofsaid right ball lens segment at the right viewing pupil of the secondviewer; and (ii) through said second beamsplitter, a real image of thepupil of said right ball lens segment at the right viewing pupil of thefirst viewer.
 2. An autostereoscopic optical apparatus according toclaim 1 wherein said left ball lens segment comprises an hemisphericlens and a reflective surface.
 3. An autostereoscopic optical apparatusaccording to claim 1 wherein said left image generation system comprisesa liquid crystal display component.
 4. An autostereoscopic opticalapparatus according to claim 1 wherein said right ball lens segmentcomprises an hemispheric lens and a reflective surface.
 5. Anautostereoscopic optical apparatus according to claim 1 wherein saidright image generation system comprises a liquid crystal displaycomponent.
 6. An autostereoscopic optical apparatus for displaying astereoscopic virtual image to a first viewer and to a second viewer,wherein the stereoscopic virtual image is imaged to each viewer at aleft viewing pupil and a right viewing pupil, the apparatus comprising:(a) a left image generation system for forming a curved leftintermediate image; (b) a left projection system comprising a left balllens segment, wherein the pupil of said left ball lens segment issubstantially concentric with said curved left intermediate image, saidleft ball lens segment forming a real image of said curved leftintermediate image; (c) a first beamsplitter disposed to direct saidcurved left intermediate image toward a second beamsplitter said secondbeamsplitter then directing said curved left intermediate image toward afocal surface of a first curved mirror, said first curved mirror forminga virtual image of said curved left intermediate image, and said firstcurved mirror disposed to form: (i) through said second and firstbeamsplitters, a real image of the pupil of said left ball lens segmentat the left viewing pupil of the first viewer; and (ii) through saidsecond beamsplitter, a real image of the pupil of said left ball lenssegment at the left viewing pupil of the second viewer; (d) a rightimage generation system for forming a curved right intermediate image;(e) a right projection system comprising a right ball lens segment,wherein the pupil of said right ball lens segment is substantiallyconcentric with said curved right intermediate image, said right balllens segment forming a real image of said curved right intermediateimage; (f) said first beamsplitter disposed to direct said curved rightintermediate image toward said second beamsplitter, said secondbeamsplitter then directing said curved right intermediate image towardsaid focal surface of said first curved mirror, said first curved mirrorforming a virtual image of said curved right intermediate image, andsaid first curved mirror disposed to form: (i) through said first andsecond beamsplitters, a real image of the pupil of said right ball lenssegment at the right viewing pupil of the first viewer; and (ii) throughsaid second beamsplitter, a real image of the pupil of said right balllens segment at the right viewing pupil of the second viewer.
 7. Anautostereoscopic optical apparatus according to claim 6 furthercomprising a folding mirror disposed in the optical path of the secondviewer.
 8. An autostereoscopic optical apparatus according to claim 6wherein said left ball lens segment comprises an hemispheric lens and areflective surface.
 9. An autostereoscopic optical apparatus accordingto claim 6 wherein said left image generation system comprises a liquidcrystal display component.
 10. An autostereoscopic optical apparatusaccording to claim 6 wherein said right ball lens segment comprises anhemispheric lens and a reflective surface.
 11. An autostereoscopicoptical apparatus according to claim 6 wherein said right imagegeneration system comprises a liquid crystal display component.
 12. Anautostereoscopic optical apparatus for displaying a stereoscopic virtualimage to a first viewer and to a second viewer, wherein the stereoscopicvirtual image is imaged to each viewer at a left viewing pupil and aright viewing pupil, the apparatus comprising: (a) a left imagegeneration system for forming a curved left intermediate image; (b) aleft projection system comprising a left ball lens segment, wherein thepupil of said left ball lens segment is substantially concentric withsaid curved left intermediate image, said left ball lens segment forminga real image of said curved left intermediate image; (c) a firstbeamsplitter disposed to direct said curved left intermediate imagetoward a second beamsplitter, said second beamsplitter then directingsaid curved left intermediate image toward a focal surface of a curvedmirror for forming a virtual image of said curved left intermediateimage thereby, and said curved mirror disposed to form: (i) through saidfirst and second beamsplitters, a real image of the pupil of said leftball lens segment at the left viewing pupil of the first viewer; and(ii) through said second beamsplitter and a third beamsplitter, a realimage of the pupil of said left ball lens segment at the left viewingpupil of the second viewer; (d) a right image generation system forforming a curved right intermediate image; (e) a right projection systemcomprising a right ball lens segment, wherein the pupil of said rightball lens segment is substantially concentric with said curved rightintermediate image, said right ball lens segment forming a real image ofsaid curved right intermediate image; (f) said third beamsplitterdisposed to direct said curved right intermediate image toward the focalsurface of said curved mirror for forming a virtual image of said curvedright intermediate image thereby, and said curved mirror disposed toform (i) through said third beamsplitter, a real image of the pupil ofsaid right ball lens segment at the right viewing pupil of the secondviewer; and (ii) through said second beamsplitter and said firstbeamsplitter, a real image of the pupil of said right ball lens segmentat the right viewing pupil of the first viewer.
 13. An autostereoscopicoptical apparatus for displaying a stereoscopic virtual image to a firstviewer and to a second viewer, wherein the stereoscopic virtual image isimaged to each viewer at a left viewing pupil and a right viewing pupil,the apparatus comprising: (a) a left image generation system for forminga curved left intermediate image; (b) a left projection systemcomprising a left ball lens segment, wherein the pupil of said left balllens segment is substantially concentric with said curved leftintermediate image, said left ball lens segment forming a real image ofsaid curved left intermediate image; (c) a first beamsplitter disposedto direct said curved left intermediate image through a secondbeamsplitter and toward a focal surface of a curved mirror, said curvedmirror forming a virtual image of said curved left intermediate imagethereby, and said curved mirror disposed to form: (i) through said firstand second beamsplitters, a real image of the pupil of said left balllens segment at the left viewing pupil of the first viewer; and (ii)through said second beamsplitter, a real image of the pupil of said leftball lens segment at the left viewing pupil of the second viewer; (d) aright image generation system for forming a curved right intermediateimage; (e) a right projection system comprising a right ball lenssegment, wherein the pupil of said right ball lens segment issubstantially concentric with said curved right intermediate image, saidright ball lens segment forming a real image of said curved rightintermediate image; (f) said first beamsplitter disposed to direct saidcurved right intermediate image toward the focal surface of said curvedmirror, said curved mirror forming a virtual image of said curved rightintermediate image thereby, and said curved mirror disposed to form: (i)through said second beamsplitter, a real image of the pupil of saidright ball lens segment at the right viewing pupil of the second viewer;and (ii) through said second beamsplitter and said first beamsplitter, areal image of the pupil of said right ball lens segment at the rightviewing pupil of the first viewer.
 14. A method for displaying anautostereoscopic virtual image to a first viewer and to a second viewer,wherein the autostereoscopic virtual image is imaged to each viewer at aleft viewing pupil and a right viewing pupil, the method comprising: (a)forming a curved left intermediate image; (b) projecting a real image ofsaid curved left intermediate image through a left ball lens segmenttoward a focal surface of a first curved mirror, said first curvedmirror forming a virtual image of said curved left intermediate image,and said first curved mirror disposed to form: (i) through a firstbeamsplitter, a real image of the pupil of said left ball lens segmentat the left viewing pupil of the first viewer; and (ii) through a secondbeamsplitter, a real image of the pupil of said left ball lens segmentat the left viewing pupil of the second viewer; (c) forming a curvedright intermediate image; (d) projecting a real image of said curvedright intermediate image through a right ball lens segment toward afocal surface of a second curved mirror, said second curved mirrorforming a virtual image of said curved right intermediate image, andsaid second curved mirror disposed to form: (i) through a thirdbeamsplitter, a real image of a the pupil of said right ball lenssegment at the right viewing pupil of the second viewer; and (ii)through said second beamsplitter, a real image of the pupil of saidright ball lens segment at the right viewing pupil of the first viewer.15. A method for displaying an autostereoscopic virtual image accordingto claim 14 wherein the step of forming said curved left intermediateimage comprises the step of controlling an area spatial light modulator.16. (cancelled)
 17. A method for displaying an autostereoscopic virtualimage to a first viewer and to a second viewer, wherein theautostereoscopic virtual image is imaged to each viewer at a leftviewing pupil and a right viewing pupil, the method comprising: (a)forming a curved left intermediate image; (b) projecting a real image ofsaid curved left intermediate image through a left ball lens segmenttoward a focal surface of a first curved mirror, said first curvedmirror forming a virtual image of said curved left intermediate imageand said first curved mirror disposed to form: (i) through a first and asecond beamsplitter, a real image of the pupil of said left ball lenssegment at the left viewing pupil of the first viewer; and (ii) throughsaid second beamsplitter, a real image of the pupil of said left balllens segment at the left viewing pupil of the second viewer; (c) forminga curved right intermediate image; (d) projecting a real image of saidcurved right intermediate image through a right ball lens segment towarda focal surface of a second curved mirror, said second curved mirrorforming a virtual image of said curved right intermediate image and saidsecond curved mirror disposed to form: (i) through said first and secondbeamsplitters, a real image of the pupil of said right ball lens segmentat the right viewing pupil of the first viewer; and (ii) through saidsecond beamsplitter, a real image of the pupil of said right ball lenssegment at the right viewing pupil of the second viewer.
 18. A methodfor displaying an autostereoscopic virtual image to a first viewer andto a second viewer, wherein the autostereoscopic virtual image is imagedto each viewer at a left viewing pupil and a right viewing pupil, themethod comprising: (a) forming a curved left intermediate image; (b)projecting a real image of said curved left intermediate image through aleft ball lens segment toward a focal surface of a curved mirror, saidcurved mirror forming a virtual image of said curved left intermediateimage and said curved mirror disposed to form: (i) through a first and asecond beamsplitter, a real image of the pupil of said left ball lenssegment at the left viewing pupil of the first viewer; and (ii) throughsaid second beamsplitter and a third beamsplitter, a real image of thepupil of said left ball lens segment at the left viewing pupil of thesecond viewer; (c) forming a curved right intermediate image; (d)projecting a real image of said curved right intermediate image througha right ball lens segment toward said focal surface of said curvedmirror, said curved mirror forming a virtual image of said curved rightintermediate image and said curved mirror disposed to form: (i) throughsaid third beamsplitter, a real image of the pupil of said right balllens segment at the right viewing pupil of the second viewer; and (ii)through said second beamsplitter and said first beamsplitter, a realimage of the pupil of said right ball lens segment at the right viewingpupil of the first viewer.
 19. A method for displaying anautostereoscopic virtual image to a first viewer and to a second viewer,wherein the autostereoscopic virtual image is imaged to each viewer at aleft viewing pupil and a right viewing pupil, the method comprising: (a)forming a curved left intermediate image; (b) projecting a real image ofsaid curved left intermediate image through a left ball lens segmenttoward a focal surface of a curved mirror, said curved mirror forming avirtual image of said curved left intermediate image and said curvedmirror disposed to form: (i) through a first and a second beamsplitter,a real image of the pupil of said left ball lens segment at the leftviewing pupil of the first viewer; and (ii) through said secondbeamsplitter, a real image of the pupil of said left ball lens segmentat the left viewing pupil of the second viewer; (c) forming a curvedright intermediate image; (d) projecting a real image of said curvedright intermediate image through a right ball lens segment toward saidfocal surface of said curved mirror, said curved mirror forming avirtual image of said curved right intermediate image and said curvedmirror disposed to form: (i) through said second beamsplitter, a realimage of the pupil of said right ball lens segment at the right viewingpupil of the second viewer; and (ii) through said second beamsplitterand said first beamsplitter, a real image of the pupil of said rightball lens segment at the right viewing pupil of the first viewer.